change MtxOrb kyboard mapping code to use KeyMap_<X>=<name>

docs/lcdproc-user/drivers/mtxorb.docbook

@@ -1,5 +1,5 @@
 <sect1 id="MtxOrb">
-<title>The Matrix Orbital Driver (MtxOrb)</title>
+<title>The MtxOrb Driver</title>
 
 <para>
       This section covers the installation process for the Matrix Orbital LCD
@@ -209,6 +209,8 @@
 	</sect4>
       </sect3>
 </sect2>
+
+<!-- This is already covered in bookinfo.docbook
 <sect2 id="MtxOrb-copy">
 <title>Copyright</title>
 
@@ -220,6 +222,7 @@ This section was originally part of the lcdproc.sgml file by William W. Ferrell
 Slightly modified in order to include it in this document March 2002, Rene Wagner <email>reenoo@gmx.de</email>
 </para>
 </sect2>
+-->
 
 <!-- ## Matrix Orbital driver ## -->
 <sect2 id="MtxOrb-config">
@@ -328,6 +331,43 @@ Slightly modified in order to include it in this document March 2002, Rene Wagne
   </para></listitem>
 </varlistentry>
 
+<varlistentry>
+  <term>
+    <command>KeyMap_<replaceable>LETTER</replaceable>=</command>
+    <arg choice="plain"><replaceable>KEY</replaceable></arg>
+  </term>
+  <listitem>
+    <para>
+    Matrix Orbital displays support keypads with up to 25 keys, which return
+    one of the letters <literal>A</literal> - <literal>Y</literal> for each
+    pressed key.
+    </para>
+    <para>
+    These settings allow to map the letter <replaceable>LETTER</replaceable>,
+    that is generated by the display when a key is pressed, to be mapped to
+    a key name <replaceable>KEY</replaceable> that <command>LCDd</command>
+    can understand (see <link linkend="menu-section" endterm="menu-section.title"/>
+    for more information).
+    </para>
+    <para>
+    There is no default key mapping; if no keys are mapped in the
+    <filename>LCDd.conf</filename> config file, the display is treated
+    as if it had no keys attached.
+    </para>
+    <example id="MtxOrb-config-keymap-example">
+      <programlisting>
+      KeyMap_A=Left
+      KeyMap_B=Right
+      KeyMap_C=Up
+      KeyMap_D=Down
+      KeyMap_E=Enter
+      KeyMap_F=Escape
+      </programlisting>
+    </example>  
+  </listitem>
+</varlistentry>
+
+<!--
 <varlistentry>
   <term>
     <command>LeftKey=</command>
@@ -361,6 +401,7 @@ Slightly modified in order to include it in this document March 2002, Rene Wagne
     <literal>A</literal> - <literal>F</literal>.
   </para></listitem>
 </varlistentry>
+-->
 
 <varlistentry>
   <term>